Alex Klein had been principal oboist at the CSO before – from 1995 to 2004, when he had to resign due to the effects of focal dystonia. After a dozen years of recovery and retooling his technique, Klein re-auditioned for and returned to his old job last year, with the usual two-season probationary period. But the musicians’ tenure review committee and music director Riccardo Muti (who has final say) decided last month not to keep Klein on.